Pneumatic-type aircraft landing gear



Sept. l2, 1950 v. N. BRADEN TAL 2,522,340

PNEUMATIc-TYPE AIRCRAFT LANDING GEAR Filed Nov. 21, 194e 2 sheets-shea 1I N V EN TOR. VALLY N. BRADEN FERN E. ENSLEY BY -6 ,www

ATTORNEY Sept. l2, 1950 v. N. BRADEN ETAL.

PNEUMATIc-TYPE AIRCRAFT LANDING GEAR 2 Sheets-Sheet 2 Filed NOV. 2l,1946 RRA! FIG

FIG. 4

INVENTOR.

VALLY N. BRADEN FERN E. ENSLEY ATTCRNEY Patented Sept. 12, 1950 UNITEDSTATES PATENT` oFFlcl:4 t

Vally N. Braden, New Haven, Conn., and Fern E.

'Ensley, Akron, Ohio, assignors to Wingfoot Corporation, Akron, Ohio, acorporation of Delaware Application November The present inventionrelates to a pneumatictype universal landing gear for aircraft'.A 'Moreparticularly, the invention isv concerned with a form of inflatableaircraft landing ,gear fabricated from rubberized fabric materialtogether with a mounting means therefor.

The landing gear of the present invention is particularly advantageouslyemployed on helicopters and other similar forms of aircraft to enablesuch'shipsto land on and take off from a landing surface Whetherit beland or Water. It iswell vknown in the operation of helicopter aircraftthat difficulty is experienced in landing and take-off due to thepresence of extraordinary static and dynamic loads. Thus, the presentinvention contemplates a multiple comparte mented structure inWhich'certain of the inflatable compartments are designed to take theforces induced by the operation of the motor'sof the craft While at restWhile others absorb' thel dynamic load of the aircraft while engaged inland-y ing and take-off operations generally.

It is, therefore, an object of thepresent inven tion to provide a formof multi-compartmented inflatable landing gear for use in aircraft.

It is another object of the present invention to provide a pneumatic oatcapable of servingV both as a landing gear and as a notation gear foraircraft, particularly aircraft of the helicopter type.

Itis a further object of the invention to provide a universalpneumatic-'type landing gear 'which will be capable of absorbing alldynamic 'loads incident to the aircraft in its landing and takeo ifoperations from any available landing surface.

Another and still further object of the present invention is to providea satisfactory and ladvan` tageous means for mounting the floatstructures upon the average commercially-builtplane. It is a stillfurther object of the present invention to provide a form ofl universallanding` gear for aircraft which, besides possessing al1 of theforegoing important attributes, has the added advantage of being capableof being manufactured economically and in large numbers to enable thecost thereof-to be low. y

Other objects and advantages of the floatstructure of the presentinvention Will become apparent asA the description of the principles ofthey present invention proceeds. l l l, n

Fig. l represents a plan view of oneform of float structure embodyingthe principles of the present invention. Fig. 2 is a side elevationv ofthe float structure shown in Fig. 1. Fig. 3. is a vertical cross-sectiontaken through tlfie'nfloatl structure of Fig. 2 along the line 3--3therein..

21, 1946,v Serial No. 711,454

9 Claims. (Cl. 244-.-105) Fig. 4' is a distorted vertical cross-sectioncorre-l sponding generally to Fig. 3 illustrating the action of thefloat structure When at rest on a landing surface.' Fig. 5 is a planview of a modified form of float structure corresponding generally tothat of Figs. l and '2. Fig. 6 is a vertical cross-section taken alongthe line 6-6 in Fig. 5.

The landing gear or `float structure of the pres@- ent invention isidentified generally by the reference character I. The float structureIyis'fabricated from rubberized fabric'material in the form of agenerally cylindrical portion 2 having substantially hemi-sphericallyshaped endsy 3. `The generally cylindrical portion 2 embodies the infternally disposed fluid-tight iniiatablecompart=- ments 4, 5, and 6. lAs will be seen from Fig. 3, the compartments 4' and 5' aresubstantially identical in `shapefand disposed in mutually parallelcontiguous relation; The rubberized fabric material 'l forms the enclo`v sureWall of the compartments 4 and 5 While the common Wall ormembrane 8 serves to define the separate compartments from each otherand secured at its ends to the end portions 3. The compartment 6 isformed by the rubberized fabric envelope 9 which cooperates With thefabric :1 to enclose the same.

The fabric envelope 9 is advantageouslyr secured to the outerfabr'icWall portion 1 as at 'I0 and the joint is sealed vby means of crotchtapes I| The lowermost arcuate outer surface of the fabric envelope 9 isprovided 'with a chafer strip assembly I2 Whichserves to prolong thelife of the float structure I by protecting the same at points ofextreme Wear. The chafer strip assembly I2 embodies a tough Wearresistant rubberized fabric strip I3 with a cushion strip I4 insertedtherein against the surface of the envelope 9 with narrow tapes I5protecting the marginalL edges of the Wear strip I3. It will beunderstoodthat the Wear strip I3 may also be made of a." toughvulcanized rubber stock, provided it does not materially affect theweight of the fioatrstruc-e ture I.

`At each end of the compartments 4 and-Svisi located avertical bulkheadmember I6 (see Fig.:

2) disposed internally of the cylindrical portion 24 at thejoint thereinformed by the end portions 3.

The compartments d and 5 taperI inwardly beyond` the bulkheads I6 tojoin with the end portions 3. Similar vertical bulkheads I1 may beemployed chambers. A corresponding number of valves I8 fol1 theadmission of fluid under pressure to each chamber of the compartments 4and 5 are secured to the external wall of the fabric `I.

The compartment 6 may advantageously be interconnected with the interiorof the hernispherical yend lportions ,3. The compartment 6, thusextending from fend to end of the float structure I, is advantageouslyinflated in its entirety by means of a valve I9. If it is found to bedesirable, suitable bulkheads may be provided in the compartment 6 todivide the same into smaller compartments, although this constructionmay affect the flexibility of the base .of `Vthe float structure I tosome extent.

The float structure I may be mounted upon the aircraft in any suitablefashion. One form of mounting which is highly advantageous employs thestandard gear or connections of the aircraft for mounting a rigid plateor saddle `ZIJ which may be fabricated from aluminum, magnesium, or,other metallic alloys as -Well as any other suitable strong 'formablematerial to conform to the shape of the upper surface yof the floatstructure I. In this case, the saddle is of arcuate form incross-section.

.Thesaddle 2D has Va felt chafer strip 2| disposed between said saddle.and the surface ofthe fabric 1 -to prevent undue wear .and chang of thefabric 1 by the saddle, The saddle 210 is held in place by means 4of apocket 22 into which an end of the saddle nts adjacent the forward .end`of the float structure i. The fabric strip rv2l and the saddle 20 aresecurely held in place by means of a lacing cord 24 laced lthrough eyes25 in the lacing strip 26 and apertures -21 in the marginal edges of thesaddle 20.

In use, the float structure I is inflated with a suitable duid underpressure, ordinarily air. For most advantageous operation of the floatstructure I, the compartments 4, 5, and 6 are inflated with air underpressure, the pressure of the `air within the compartments 4 and 5 beinggreater than the pressure i-n the compartment 6, The lower pressure ofthe air in compartment 5 enables it to deflect under load when incontact with the landing surface to support the aircraft and to providea cushion therefor. The compartment 4 and 5, being less flexible, serveto provide an added factor of safety and a positive support althoughordinarily these compartments Ydo not actually contact the landingsurface excepting under emergency conditions.

Such float structures I contemplated by the invention are particularlyadvantageously adapted to be employed with helicopter-type aircraft toenable the ship to land on and take on from land or water. The loadingstaken by compartment vti in actual operations include the weight `of theplane when in contact with the landing surface as Well as the dynamicforces `set up in the `craft While it is at rest with the motors inoperation. Thus, the low pressure compartment E cushions the effect ofthe dynamic forces set up in craft While the high pressure compartments4 and 5 absorb the dynami load of the aircraft in the landing andtake-oil operations after the cushioning effect of the compartment E iscompletely taken up.

It has been found that the air pressure employed in the ination of the.compartment 6 should be in the neighborhood of 60 per cent of theinflation pressure of the compartments 4 and 5 for satisfactory results.It is also desirable to have the volume of the compartments 4 and 5 beroughly in the proportion of the volumes illustratecl in Fig. 3 of thedrawings to insure the maximum cushioning effect. These features, aswill be readily understood, are capable of some adjustment and revisionwithout materially affecting the efficiency of the oat structure I,

`it being understood that any change in the crossv,sectional dimensionsof the compartments will necessitate some variation in the inflationpres- .sures for these compartments.

It is also necessary to take into consideration -in the designof thefloat structures of the invention, with particular emphasis upon thecrosssectional dimensions of the several inflatable compartmentsthereof, the altitude range of the aircraft on which the floats are tobe employed. Wide Variations in altitude tend to build up increasedpressures in the inated compartments due to the diminution of theexternal atmospheric pressure at high altitudes. Thus, it is necessaryto insure that the fabric employed in the fabrica- ,tionlof the`floatstr'ucture I `iscf sufficient strength to withstand the stressesinvolved.

The oat structure I, when in contact with a landing sur-face, assu-mes ashape closely approximating that illustrated in Fig. 4 of the drawings.The weight of the craft itself 4causes the low pressure compartment -6to atten out to an extent such that the rubberized fabric yenvelope y9defining that compartment nearly contacts the fabric Vmaterial 1enclosing the internally disposed high pressure compartments y4 and `5.In this distorted or flattened form the low pressure compartment -6 actsas a cushion for the .absorption of the dynamicforces created chiefly bythe action of .the rotor blades when the .ship so equipped is at restupon a landing surface.

The plate 0r saddle 20 is .so designed that it insures a broad surfaceof contact with the top portion of the neat structure I to enable a moreeven distribution vover the entire oat structure of the forces set up inthe aircraft on lwhich the floats are mounted under `all-operatingconditions. For most satisfactory results in the design of such landinggear as that to which the invention relates, the product of the area ofcontact between the saddle 20 and the high pressure compartments 4 and 5of the float structure I vand the uid pressure in these compartmentsmust always be in excess of the product of the area .of contact of thebottom surface of the float structure with the landing surface and thefluid pressure in the low pressure compartment 6, If the reversecondition .is obtained, the saddle 20 will cause the forces incident tothe operation of the craft to be concentrated at the vcentral axis ofthe float structure I resulting in the crushing in of the top surfacethereof or in destruction of the saddle itself.

The design .conditions previously discussed can best be illustrated by amathematical formula. Where A represents the area of the contact surfaceof the saddle 2l] with the top of the oat structure I in square inches,P is the pressure of the fluid in the high pressure compartments 4 and 5in pounds per square inch, B is the area of contact of the low pressurecompartment 6 with the landing surface in square inches, andv Qrepresents the pressure of the fluid in the compartment 6 in pounds persquare inch, the formula AP BQ governs the optimum design of the saddlestructure 2l! and the oat structure I. Unless the foregoing relation iscarefully calculated and maintained in the design of the saddle 20 andthe float structure I, the landing gear will be unstable.

.is defined-by fabric-enclosure 3|.

. jfA modification of-the structure fof Figs-l to4, inclusive; isillustrated! in:` Figs;v 5 and 6- and :the same-principles -of theinvention.fare..involved tl'ierein.-` The modied structure-.embodiesonly;.;a single highlpressure compartment28 disposed internally of theIlow pressure compartment 29 and substantially .completely encircledbythe latter. 'Ihe compartment 29 is formed within the rubberizedfabricgenclosure while the compartment 28 The chafer strip assembly 32is identical to the assembly l2 of the float structurel; i f 1 .Y Thevalves 33 for admitting iiuid under pressure to the compartment 29 aswell asthe valve (not shown) for inflating the compartment 28 aresubstantialh7 the same as those employed in the form-,.of-oat structureI illustrated in Fig. 3. f The saddle Aand its associated mountingfelements differ Vprimarily in the shape ofthe saddle itself as `yvillbeseen wfrom a comparison of the parts-between Figs.'3 and 5. If desired,two narrowfelt strips 35 may also be substituted for the single strip 2I.

Other modifications mayy be'l -made in the apparatus of the inventionwithout in any way' departing from the; spirit orfscopeofthe invention.;,s-Whilezfin@accordance with thev patent statutes certain embodimentsof the invention have been illustrated and described in detail, it is tobe particularly understood that the invention is not limited thereto orthereby, but that the inventive scope is defined in the appended claims.

We claim:

1. A pneumatic-type universal landing gear for aircraft comprising aninflatable structure embodying a plurality of hollow generally tubularcompartments of rubberized fabric material arranged in mutually parallelrelation to each other, one of said compartments being so disposed thatit at least partially encompasses the others; means for inflating eachindividual compartment with fluid under pressure to provide a pressuredifferential between the several compartments; and saddle meansconforming to the contour of the inflatable structure for mounting thesame on the aircraft and distributing to the several compartments thestatic loads as well as the dynamic loads induced inthe aircraft in itslanding and take-off operations and while at rest on a landing surfacewith its motors operating.

2. A pneumatic-type universal landing gear for aircraft comprising aninflatable structure embodying at least two hollow generally tubularcompartments of rubberized fabric material arranged in mutually parallelrelation to each other with one of said compartments being so disposedthat it substantially completely encompasses the other means forinflating each individual compartment with fluid under pressure toprovide a pressure differential between the several compartments; saddlemeans conforming generally to the contour of the inflatable structurefor mounting the same on the aircraft, said saddle means extendingsubstantially coextensively withv compartment .of the inflatableystructur-'e opposite the` position ofthe saddle means; and meansfordemountablyt attaching said inflatable structure to.`said saddle means.f f .V e 4. A. saddleformounting on aircrafta, pneumatic-typelandingfgear embodying at least two generally, tubular' compartments' ofrubberized fabric-and ,theilika one ofA which hasfa higher 'pressure -kthan `the other, l.one ,ofsaid -compartments being engaged by theAsaddle and vone forgcontact with ,a` landingsurface, said saddlehaving,y anI arcuateA su'rfa'sle'v conforming generally to the` shape,of the kcompartrnent whichy it contacts when assembled and havingv asurface area which exceeds the product of the'ratio of the fluidpressure in the low pressure compartment to the fluid pressure in thehigh pressure cornpartment and the area of the compartment incontactwith the landing surface when the craft is at rest thereon.

` 5. A. saddle for mounting on aircraft a pneumatic-type landing gearembodying a pair of contiguously arranged generally tubular compartmentsof rubberized fabric forming the top portion of the gear and a thirdrubberized fabric compartment associated therewith for contact with alanding surface, the pair of compartments being inflated at a higher uidpressure than the third compartment, said saddle having a generallyarcuately shaped surface closely conforming to the shape of the outerperipheral walls of the pair of tubular compartments and extendingsubstantially coextensively therewith, said surface having an area whichexceeds the product of the ratio of the fluid pressure in the lowpressure compartment to the fluid pressure vin the high pressurecompartment and the area of the third compartment in contact with thelandingy surface when the craft is at rest thereon.

6. A universal landing gear for helicopter aircraft and the likecomprising a pneumatic-type oat structure embodying a pair ofcontlguouslyl arranged generally tubular inflatable compartments ofrubberized fabric forming the top portion thereof and a commoninflatable compartment extending in parallel relation to theaforementioned compartments and forming the end portions therefor forcontact with a landing surface, said common compartment having a lowerfluid pressure than the pair of compartments; a saddle having agenerally arcuate mounting surface extending substantially coextensivelywith a pair of high pressure compartments and closely tting the outerwalls thereof, said mounting surface having an area which exceeds theproduct of the ratio of the fluid pressure in the common. compartment tothe fluid pressure in the pair of compartments and the area of thatportion of the common compartment which contacts the landing surfacewhen the craft is at rest thereon;

and ,means disengageably securing the oat structure to the saddle.

` 7. Inl a helicopter, a body having operating parts that vibrate undersome conditions, in combination with means for preventing suchvibrations from being transferred to a supporting surface for saidaircraft and transferred back to said aircraft in phase with suchvibrations consisting of one or more floats, each float having a pair ofupper cells and a lower cell containing gasl at different pressures indierent cells, said lower cell having a bottom Wall comprising a landingsurface engaging portion and connection means between the upper cellsand said body. 8. A oatfor helicopters comprising a first variablevolume chamber having a bottom wall constituting a landing surfaceengaging portion and containing a gas at a pressure to provide a naturalvibration for its Walls at a rst frequency, and at least one othervariable volume chamber above said rst chamber having means forconnecting the float to the body of the helicopter and adapted tocontain agas at a diierent pressure to provide a natural vibration forits walls at a second frequency.

9. A float for a helicopter comprising an elongated envelope ofexpansible material having longitudinally extending vpartitionskdividing said 8 iloatV into 'a plurality of upper side-by-side' cellsand a' single lower cell, the upper Wall of said lower cell'constituting the bottom walls of said upper cells and the bottom wallof said lower cell constituting a landing surface contacting portion,and means carried by the external Walls of said upper cells forconnecting said iloat to a helicopter.

VALLY N. BRADEN.

FERN E. ENSLEY.

REFERENCES CITEDl The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number vName Date 1,317,741 Turnbull Oct. 7, 19192,349,584 Arnstein May 23, 1944 2,391,326 McKinley Dec. 18, 19452,465,193 Boyle Mar. 22,1949

FOREIGN PATENTS Number Country Date 115,260 Great Britain Apr. 29, 1918126,934 `Great Britain May 14, 1919 302,232 Great Britain Mar. 5, 1930

